Distillation of tar



Oct. 18, 1932. E. H. ELLMS DISTILLATION OF TAR 5 Sheets-Sheet l FiledSept. 17 1928 INVENTOR v %//M% ATTORNEYS ww@ @8&8 n

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Oct. 18, 1932. E. H. ELLMS DISTILLATION OF TAR I5 Sheets-Sheet 2 FiledSept. 1'?, 1928 r/ca'/ Freak/72175K ATTORNEYS 01.18,1932. l EH ELLMS1,883,642

DISTILLATION OF TAR Filed Sept. 17, 1928 5 Sheets-Sheet 'o' ATTORNEYPatented Oct. 18, 1932 VUNITEDl STATES PATENT OFFICE EDWARD H. ELLIS, 0FENGLEWOOD, NEW JERSEY, ASSIGNOB, TO THE BARRET!!!- COI- PANY, OF NEWYORK, N. Y., A CORPORATION 0F NEW JERSEY -nIsrrLLaTIoN oF 'TAB AApplication mea september 17, 192s. seal ne. 306,330.

This invention relates to improvements in the distillation of tar byutilizing the heat available in the gases lproduced incoal-carbonization plants,and particularly tothe production of clean oilfractions of definite character fromysuch gases. The invention will bedescribed especially with reference toits application to cok ovens. J

In the ordinary operation of by-product coke ovens the gases produced bythe coking -operation pass from the individual ovens through uptakepipes and goose-necks to a collector main common to the ovens of thebattery. The foul gases leave the ovens at high temperature, e. g., 600to 700 C. or higher, and carry a considerable proportion of volatilizedtars and oils as well as solid particles of coke, coal, carbon and otherimpurities. i rapidly by the application of sprays of ammonia liquor orammonia liquor and tar in the goose-necksA and collector main, the heatin the gases being thereby dissipated and lost.

.The rapid cooling causes separation of tar containing the heavier oilsin the collector main. Further cooling is effected in the' cross-overmain and in the condensing system connected therewith and an additional-quantity of tar or tarry oil is thus separated.

The collected tars and tarry oil are shipped ordinarily from thecoke-oven plant to a, tar-L distillation plant for distillation andseparation of the oils andthe production of pitches of varyingqualities. The expense of handling and of distilling the tar and oiladds to the cost of'production of distillation products.

. It is the object of the present invention to provide a method andapparatus'which permits the distillation of t-arat a coke-oven plant,the utilization of the heat of the cokeoven gases for that purpose, andparticularly the recovery of efinite fractions of clean oils directly bysuch distillation, together with pitches having the various qualitiesand characteristics required by the trade..

According to the present invention the i heat of the coke-oven gases asthey-come from the coke ovens is utilized to distill tar and to separatevaporizable oils therefrom by sprayi Ordinarily the gases are cooled ingor otherwise bringing the tar into intimate contact with the hotcoke-oven gases. The desired vdistillation can be effected in varioustypes of apparatus as, for example, in a collector main or 'inuptake-pipe stills as described in the application-'of George E.Brandon, Serial No. 154,740, filed December 14, 1926, or in any othersuitable apparatus in .which intimate contact between the hot gasesandthe tar can be obtained. The intimate contact between the tar and thehot coke-oven gases cools the gases and at-the same time the tar is moreor less distilled. Partial condensation of the condensable constituentsin the gases, more particularly those of a tarry character, results. Thescrubbing ofthe gases with tar tends `to separate such tarryconstituents. At the same time the gases are enriched with vapors of themore volatile constituents, i. e., oils derived from the distillation ofthe tar.

. The dew points of the gases for the several constituents carriedtherein as vapor are lower than the normal boiling points of theseconstituents, and by suitable regulation of the temperature of the gasesduring the distillation and especially during the subsequent treatment.of the gases vals hereinafter described it is possible to retain thedesired oils in vapor form therein while the tarry constituents arecondensed. -Thus, by sutliciently lowering the temperature of the gasesduring distillation in the collector main, for example, all orsubstantially all of the tarry constituents can be converted into theliquid phase carried by the gases is known as tar fog It is removed fromthe gases with diiiiculty and to a greater or less degree persists evenlll in the fuel gases, i. e., the linally purilied gases. ln the processof my invention, a large portion ol this tar fog is removed by the tarwhich is brought intimately in contact with the hot gases.

Some oi the tar which is present in the gas stream leaving the ovens maystill remain in the gas stream alter it has been subjected to intimatecontact with the tar introduced jfor distillation. 'lhe quantity of tartog lett in the gas is small and when good contact has been providedbetween the tar and gases in the distilling operation, it is not usuallysucient to adect the quality ot the distillate oil. I

'llhe entrained tar and tar tog can, for example, be separated readilyby passing the gases thru an electrical precipitator such, lor instance,as the well known Cottrell precipitator, the precipitator being operatedat substantially the temperature required to maintain the desired oilconstituents in the vapor phase, that is to say, at a temperature higherthan the dew point ot the gas for the most readily condensable desiredoil constituent therein.

The electrical precipitator, is, however, not essential to theproduction of clean distillate oils. A substantial proportion of theentrained tar and tar fog in the gases leaving the zone of intimatecontact of the gases with ,the tar to be distilled can be removed bysubfleeting the gases to a second zone of intimate.

contact with tar, this second zone of contact being characterized by thefact that the tar is warm and exposed over large surfaces to the gases.Such a condition may, for example, be realized by causingy the gases, onleaving the irst zone ot contact, to pass thru a tower tilled withsuitable packing over which a current of warm tar is flowing in suchquantities that the gases are not cooledbelow the dew point for thedesired oil constituent. llt should be noted that the dew point, or moreproperly the equilibrium point, depends on the material with which theoil vapor bearing gases are in contact and that it is lower when incontact with tar than when in contact with hard pitch. A

The gases, which have been thus cleaned if desired, will, upon totalcondensation, yield a mixture of oil constituents. The dew points of thegases for these several constituents are, however, different and incarrying out the present invention advantage is taken of this differenceby subjectingthe clean gases to cooling in successive stages by indirectheat exchange with liquids boiling at constant temperatures. This heatexchange can be e'ected in suitable condensers through which the hotgas/es are passed in heat exchange relation with the selected liquidsurrounding, for example, the tubes of the condenser. By selecting asuitable liquid and by venting the space in which the liquid ismaintained inesatta to a suitable condenser wherein the vapors producedare condensed and recovered, the temperature to which the clean hotgases are cooled in each such stage may be maintained constant and a:traction of the vapors conn tained in such gases which condenses atthat temperature may be thus recovered. The condensed constant boilingliquid may returned to its condenser for further cooling of the hotgases.

@ne or more such condensers may be uti= lized with liquids boiling atdifferent temperatures and the gases may be subjected thereafter to inalcondensation with cooling liquid such as water at a temperature whichensures the separation of substantially all ot the remaining desiredvapors from the gases. For example, when making pitch ot 4009 l?.melting point, the clean gases may escape from the electricalprecipitator or the second stage tar scrubbing at a temperature I offrom 2400 to 3400 C., depending upon the manner of conducting theoperation.. The gases may be subjected then to cooling in a suitablecondenser to a temperature of, for example, 170o to 185 C. by heatexchange with a suitable condensing agent. Such a condensing agent maybe a coal tar naphtha fraction having a boiling range oi 160 to ll" C.rllherealter the gases may be further cooled to a temperature, forexample, ot ll5 C. by heat exchange with another liquid such as toluolhaving a boiling point ot about l`l0 C. lt will be understood that theliquids selected as condensing agents will depend upon the temperatureswhich are to be maintained in the respective condensers and that theselection will be made inv view of the character or" the fractions to beseparated from the cleaned coke-oven gases.

'lhus in the operation as described, the clean gases may be subjected tosuccessive cooling to the indicated temperatures tor the purpose ofseparating first a lieavy creosote oil and thereafter a light creosoteoil. Further riooling of the gases by heat exchange with a cool`= ingliquid such as water or ammonia liquor, for example, will result inseparation ot`car= bolic oil. Thereafter the gases can be conducted thruthe usual apparatus for the recovery of ammonia, light oils, etc.

When particularly well deined fractions are desired, a tfractionatingvsection may be included in the constant boiling liquid condensers. rl`hefractionation section may be composed of plates ot the known type or otsuitable grids or packing. e tractionating section will be located atthe bottom of the condenser in such a way that the condensate from thetubes will run back over the plates or packing and the hot gasesentering the condenser will be first forced to pass thru the plates orpacking, thereby bringing the condensate and the hot gases into heatexlll@ llll

'heat exchange with a cooling agent circulated thru the condensers forthat purpose.

The cooling agent may preferably be a liquid which is` to be distilledimmediately after leaving the condensers. The liquid will be preheatedand this will provide' a partof the heat which would otherwise have tobe supplied in the distilling equipment. A saving in heat is thereforeeii'ecte'd. Thus tar maybe used as the cooling agent in the'con--densers; the tar will thereby be preheated and may be partiallydehydrated and may then be conducted into the distilling equipment. Theheat required to be supplied to the distilling equipment will be lessdue to the fact that the tar is preheated. The capacity of the gasesfrom a given number of ovens to distill tar is thereby increased. Theheat available in such gases is thus utilized eiectively for the purposeof the invention and 1 the distillation and recovery of the desired oilroducts is accomplished economically.

he cooling of the vapors may be effected `with a cooling agent otherthan tar. Thus ammonia liquor may be used as the cooling agent and isthereby preheated and brought into a suitable condition for distillationvthe ammonia still. In a like manner, benzo' lized straw oil or otherabsorbent oil, may be used as the coolin agent and be thereby preheatedand brougt into a suitable condition for distillation. If oil 4fractionsare A to be v redistilled, these oil fractions may be used as thecooling agent and be thereby preheated and prepared for distillation. Ifthe oil fractions are very low boiling, they may even be distilledv bymeans of the heat recovered in the condensers.

The distillation of tar by means of the hot coke-oven gases will bedescribed more particularly with reference to the operation of acollector main although as hereinbefore indicated other apparatus may beadapted for the purpose of the invention. The amount of heat which isavailable in the gases from all of the ovens of the battery is manytimes that required to distill all of the tar and oil recoveredsimultaneously from the battery.

i Normally, therefore, it will not be necessary to use the gases fromall of the ovens unless.

a quantity of tar is available from other sources or unless'tar from thebattery has been accumulated. The invention is not limited, however, tothe distillation of tar from a vsingle battery of ovens. Tar from otherovens or from other sources such as' gas retorts, vertical retorts andwater-gas sets may be distilled in accordancewiththe invention. It is tobe understood, therefore, that provision can be made for utilizing theheat from any desired number of ovens. Usually,- however, it issulicient to employ the gases from only a few of the ovens and'these canbe connected convenientl to a short collector main or other distillationapparatus in which ythe distillation is conducted.

With such an apparatus, the coke-oven battery and by-product recoverysystem will not require substantial modification, that is to say, theovens of the battery may be connected to the usual collector main and acrossover main may convey the gases from the c ollector main to thecondensing system in which tar and oils are normally separated from thegases. For the purpose of distilling tar a selected number of ovens maybe connected,

for example, by separate uptake Apipes to af short collector main whichmay be disposed conveniently at the rear of the ovens, suitable valvesbeing provided to permit diversion of the gases from the ovens into theordinary collector main or into the short collector main so thatdistillation can be conducted inv the latter when desired.

The gases in the ordinary collector main maybe subjected to cooling inthe usual manner with sprays of ammonia liquor or am monia liquor andtar and the tarry constituents thus separated may be withdrawn fordistillation. The gases may be conveyed then to the usual condensers andfurther cooled the'rein to separate tarry oil constituents. The tarryois thus recovered are 'usually contaminated to a greater or less extentwith tar constituents and these tarry oils may be subjected to xdistillation with the tar re covered from the battery in accordance withthe present invention or otherwise treated to separate the constituentsthereof.

The tar or tar and 'tarry oil to be distilled may be sprayed into theshort collector main thru spray nozzles provided for that purpose andrepeatedly recirculated thru spray nozzles, thus ensuring` the ldesiredintimate contact of the gases with the tar and/or pitch therein. vAs asubstitute for or adjunct to the spray nozzles agitating devices may beprovided in the collector main to thoroughly agitate the tar therein andto throw particles thereof into the gas stream to facilitate the desiredintimate contact between the tar and.

tend to form therein will be dissolved immediately and absorbed in thestream of pitch in the bottom of the main. Pitch is drawn ed at one endof the main and tar is added at the other end and at intermediate pointsif desired at the rate required to maintain the pitch at the desiredmelting point or the gases leaving they main at the desired temperature.The pitch produced may be withdrawn and utilized as such. By regulationof the temperature of the gases and consequently the extent to whichdistillation is eect-ed in the distillation apparatus, pitches havingthe desired qualities and various products having di'erent qualities andcharacteristics may be made available for commercial use.

rlhe gases escaping from the short collector main or other distillationapparatus at the temperature requisitefor the recovery of desired oilstherefrom following the cleaning of the gases may, if desired, bedelivered at' such temperature to an electrical precipitator which isdisposed preferably closely adjacent to the collector main in order thatthe temperature of the gases may not be reduced unduly before electricalprecipitation of the tar constituents is accomplished. rllhe electricalprecipitator employed in the treatment of the gases may be of the typecommonly known as the Cottrell Iprecipitator and should be constructedso as to be capable of withstanding the high temperature to which it isl subjected in the operation as described. The

electrical precipitatorhmay be insulated advantageously to prevent lossof heat from the gases. i

The operation of an electrical precipitator as commonly used consists inpassing the gas to be treated between electrodes whose dierence inelectrical potential is very great. Experience has shown that it is bestto use a rectified alternating current. The alternating current (theprimary) is sent thru a stepup transformer to produce a high potentialcurrent (the secondary) which is then rectiied to an intermittentuni-directional current, for example, by means of a rotary converter.The rectified current is delivered from the converter to the electricalprecipitator at practically the potential at which 1t leaves thetransformer.

'llhe electrical precipitator consists commonly of a group of verticalpipes with a wire or rod in the centre of each, the pipes beingconnected to proper headers for the introduction and discharge of thegases, rlhe pipes generally constitute the positive electrodes and thewires or rods the negative electrodes. The size of the pipes may vary,but in general pipes of less than six inches in diameter are notI used.Electrical precipitators with pipes six inches in diameter using`secondary voltages rfrom 35,000 to 50,000

volts are satisfactory'tor the purposes of this invention. lt isgenerally best to operate with maximum pptential diderence(secondinesatta ary current) between the electrodes, this maximum beingjust below the break-down voltage at which arcing occurs.

rlhe eiiiciency of vthe cleaning is dependent upon several variables.Satisfactory cleaning of the gas may be accomplished if the time oftreatment is of the order of one second, although this time may bevaried Widely depending upon the character of the oil to be recoveredfrom the gases passing through the precipitator. ln working with tubes'-nine feet long and six inches in diameter, if'or example, an oilsubstantially free from all tarry constituents has been obtained with atime of treatment of from one and one-half to two seconds, that is tosay, with a gas ve-v locity of from 6 to 4.5 feet per second. This hasgiven an eiiiciency ot cleaning of approximately ninety-nine per cent.lt it is desired to collect oils containing small amounts of tar shortertreatment may be used, for example, a treatment of from 0.5 to onesecond, that is to say, with a velocity of :from 18 to 9 feet persecond.

From the electrical precipitator the gases carrying the condensablevapors can be con` ducted directly to the constant temperature condenseror through a series of such condensers. rlhe condenser or condensers maycomprise suitable casings` enclosing tubes through which the hot gasespass upwardly in heat exchange relation with a surrounding body of thecooling media which as hereinbefore indicated may be selected in view ofits boiling point to maintain a constantl temperature in the condenseras the result of boiling of the condensing medium at substantiallyatmospheric pressure. The vapor lproduced by such boiling may beconducted to another condenser which is vented to the atmosphere andcooled therein to separate the cooling media which may be returned bygravity to the constant temperature condenser. rlhe tar to be distilledmay be uti- A lized to cool the vapor and may be heated thus before itenters the short collector main,

for example, for distillation therein. If two constant temperaturecondensers are employed the gases from the first condenser are conductedthrough the second condenserin heat exchange relation with anotherliquid boiling preferably at a lower temperature to condense anotherfraction of the vapors carried by the clean gases. The cooling mediawill be vaporized and the vapor may be 'condensed to recover the coolingmedia by heat exchange with tar, tor example. |The clean gases stillcarrying some condensable constituents may be conducted then through athird condenser wherein they are subjected, for example, to direct orindirect cooling by water or ammonia liquor whereby additionalconstituents are condensed and recovered. The gases can be mingled thenif desired with those from the remaining ovens of the battery after suchgases have been subjected to coolingand condensation.

for'other purposes, the tar which is being distilled in the shortcollector main may be v conducted directlg'eto the main withoutpreheating or may preheated in a separate reheater. The liquid which isbeing' preheated in the vapor condensers will be conducted thru thesecondensers countercurrent to the order in which the condensers are arranwith respect to the hotv gas flow, so that t e entering liquid'irstcools the va rs om the lowest boiling condenser, an on' leaving .theseries /of condensers, the preheated liquid will be conducted directlyto the equipment where its. distillation is to be carried out.

The invention is of more or less general application to the distillationof tar to ro duce pitches and to recover clean oil actions. It will befurther described with reference to the preheating of tar and thecleaning of the gases in an electrical precipitator, as an example, bythe following more detailed description taken with the accompanyingdrawings whichv show apparatus embodying the invention and adapted forthe practice of the process but it is intended and will be understoodthat the invention is not limited to the apparatus as illustrated in thedrawings, in which Fig. 1 is a plan view of a portion of a coke ovenplant illustrating the application of the invention thereto;

Fig.. 2 is an enlarged sectional view of the short collector main andthe electrical precipitator connected thereto; and

Fig. 3 is an enlarged sectional view of the constant temperaturecondensers.

Referring to the drawings, 5 indicates the batteryof coke-ovens infwhlchthe individual ovens are connected by uptake pipes and goose-necks 6 toa collector main 7 having a centre box 8 from which the cross-over main9 conveys the gases and vapors to condensers 10 and 11. The gases may becooled in the collector main and in the goosenecks leading thereto byammonia liquor or ammonia liquor and tar introduced through spray noz-`zles 12 which are supplied through a pipe 13 from a source of ammonialiquor and/or tar such as a storage tank 14. Further cooling is eectedin the condensers 10 and 11 and the Ygases are delivered thence to anexhauster 15 and to the usual equipment (not shown) for the separation-of light oils and ammonia from the gases. The tar which separated inthe collector main 7 may be withdrawn from the centre box 8 anddelivered together with the tar separated in the cross-over main to a jdecanter 16 wherein the tar is separated from the ammonia liquor, thelatter being delivered tothe tank 14. The tar may be delivered to a tank17 wherein it is stored for distillation in accordance with the presentinvention'. The tarry oils separated in the condensers 10 and 11 may bewithdrawn through a pipe 1.8

to a decanter 19 wherein ammonia liquor 1s separated `from the oilmfThetarry oil may be stored then in a tank 20 and can be mingled I with thetar to be distilled in desired proporl tions or treated otherwise forthe recovery of constituents thereof. f

A short collector main 21 may be provided, for example, at the rear ofthe ovens and may be connected to the desired number of ovens by uptakepipes and goose-necks 22 whereby the hot gases are delivered to theshort collector main for utilizationptherein in the distillation of tar.The tar'to be distilled may be delivered through a pipe 23 from the tank17 to spray `nozzles 24 in the short col- -lector main 2 1 andgoose-necks 22, being therein mingled-intimately with the hot ases forthe purposeof effecting the desir distillation. To facilitate theoperation of the short collector main tar or oil or both may bedelivered thereto through a ipe 27 so as to ilow through the main andush `the bottom thereof.. `The pitch produced by the distillation maybewithdrawn through a pipel 28 for utilization as such or all 3or anyportion thereof may be recirculated through the pump 29 vand pipe 30.

The gases and vapors rulting from the distillation are withdrawn througha pipe 3-1 and are delivered to an electrical precipitator which maconsist of a shell 33 enclosing a number o tubes 34 ywhich are supportedin heads 35 and 36 within the shell. An inlet 37 near the bottom of theshell communicates with a chamber 38 which is partially separated fromthe tube section by a baille 39. An outlet 40 permits the escape ofgases from the separator after the latter have passed through the tubes.

A plurality of electrodes 41, preferably in the form of metal rodsweighted at 42, extend through the tubes and are supported from abus-bar 43 located near the upper ends of the tubes. The bus-bar 43extends at both ends into casings 44 which enclose insulators 45 ative.The form and arrangement of the. conductors in the circuit can'bevaried. y The t arrangement should be such as to supply'high form, enterthe electrical precipitator and -pa-ss through the tubes in theprecipitator,

being subjected therein to the electrical discharge which throughionization of the solid and liquid particles causes them to separatefrom the gases and condensable vapors. The separated liquids, togetherwith the solid particles, run down the inner walls of the tubes into thechamber at the bottom of theV precipitator and can be withdrawn througha pipe 46, or returned to the short collector The gases carrying thecondensable vapors escape through the outlet 40 and may be deliveredthereby to a condenser 48 comprising `a shell with tubes 49 therein thruwhich the gases pass in heat exchange relation with a body of liquiddisposed within the shell. The liquid boils at a constant temperatureand the vapor escapes thru a pipe 50 to a condenser 51 which maylikewise consist of a shell enclosing tubes 52 thru which the vaporspass. The tubes 52 may be surrounded with a suitable cooling medium suchas tar supplied thereto thru a pipe 53. rlhe vapors of the coolingliquid are condensed and returned to the condenser 48 through pipe 50.As

shown in the drawings, the tar used in the condenser 51, supplied thruthe line 53, may be tar which has been partially preheated,

vas described below. As shown, the tar escapes from the condenser 51thru a pipe '54 which connects with thepipe 23 leading to the shortcollector main. The tubes 52 communicate with the atmosphere thru anoutlet 55 so that the boiling liquid in the condenser 48 is maintainedat substantially atmosphericpressure so that the condenser opera-tes ata uniform temperature. rIhe liquid which condenses in the condenser 48is withl. drawn thru a pipe 56 to a storage receptacle `57 for thecondensate.

The cleaned gases may pass from the condenser 48 thru a pipe 58 to asecond condenser 59 comprlsing a shell and a plurality of tubes 60 thruwhich the gases pass in heat exchange relation withy a surrounding bodyof liquid boiling at a constant and lower temperature. The vapors thusroduced escape through a pipe 61 to a con enser 62 likewise compris` inga shell and a plurality of tubes 63 through which the vapors pass inheat exchange relation with a cooling liquid such as tar suppliedthrough a pipe 64 and escaping through a pipe 53. The vapors of thecooling liquid are condensed and returned to the condenser a 65i 48through pipe 61. r1`he tubes 63 of the conieaeaa denser communicate withthe atmosphere through an outlet 66 thus maintaining the pressure in thecondenser 59 at substantially atmospheric pressure. The liquid,condensed in the condenser 59 escapes through a pipe 67 to a decanter68 wherein the oil is separated from any water or ammonia liquor" whichmay be present. rlhe oil is withdrawn through a pipe 69 to a receptacle70 therefor.

The gases escaping from the condenser 59 pass through a pipe 71 to acondenser 72 which may -be of the direct or indirect type wherein thegases are subjected to va cooling medium such as water or ammonia liquorfrom the decanters 68 and 75. The condensate escapes through a pipe 74to a decanter 75 wherein the oil is separated from the ammonia liquor orwater. The oil is delivered through a pipe 76 to a receptacle 77therefor. The water or ammonia liquor from the decanters 68 and 75 maybe delivered through pipes 7 6 and 77 to a pump 78 and returned therebythrough a heat exchanger 79 to the condenser 72 for further use therein.rl`he make of water or ammonia liquor must of course be withdrawn fromthe system, for example, thru outlet pipe 73.

The gases from which the major portion of the condensable constituentshave now been removed. are withdrawn through a pipe 80 and are deliveredto the exhauster 1 5 which maintains the pressure balance in the systemand there mingled with the gases from the remaining ovens of thebattery. rllhe gases may be conducted thence through any suitableequipment for the recovery of light oils, ammonia, etc.

The tar used in the condensers may be tar from 17 or tarry oil from 20,or tar or other material may be supplied from any outside source 81. Thesame cooling medium may be used in both of the condensers 51 andy 62 andpassed therethru in succession, as shown in the drawings, or a differentmaterial may be supplied to each condenser. Where tar is employed as thecooling medium, it may advantageously be run' to the short collectormain to be distilled therein. The cooling medium need not be run to theshort collector main, as shown in the drawings, but may be put to anydesired use.

The apparatus as described permits the distillation of tar and theutilization for this purpose of a portion of the heat in the cokeovengases. It likewise permits the recovery of thel oil constituents of thegases inseparate fractions having more or less defi-l nitecharacter1stics. These fractions may be utilized for any of the purposesto which they are adapted without further treatment or they may besubjected to any desired treatment designed to modify theircharacteristics and qualities. The invention also permits the productionof Ipitch 4from the tar recovered from the battery and the character oftheV pitch can be varied by modifying the distillation to which the taris subjected. While such ratus employed therefor without departing fromthe invention or sacrificing any of the advantages thereof.

I claim 1. The process for obtaining clean oil from tar'wliich comprisesdistilling the tar by direct contact with hot coal distillation gases,

' removing entrained impurities from Athe gases at a temperature abovethe dew point of condensable oil constituents contained in the gases,cooling the resulting cleaned -hot gases and vapors by indirect heatinterchange with a bod'yof liquid cooling medium having a relativelyconstant boiling point with- -in the range of from about 110o C. toabout 1,850.0., whereby the cooling medium is kept boiling 'and thegases and vapors are cooled below the dew point of thewcondensable oilconstituents, and separately collecting thev clean oil thus condensed.

2. The method of distilling tar and recovering distillate therefrom,which comprises distilling coal tar by direct contact with hot coaldistillation gases and removing entrained impurities from the gases andthen cooling the resulting clean hot ga-ses and vapors by indirect heatinterchange with a body of toluol some of which is in the liquid phaseand some of which is in the gaseous phase in equilibrium therewith,whereby the toluol is kept boiling and the gases and vapors are cooledbelow the dew point of condensable oil constituents.

3. The method of distilling tar and recovg ering distillate therefrom byheat interchange witli a body of cooling medium with a boiling point ofapproximately 11()o C. some of which is in the liquid phase and some ofwhich is in the gaseous phase in equilibrium therewith, which comprisesdistilling coal tar by direct contact with hot coal distillation gasesand removing entrained viinpurities from the gases, then cooling theresulting clean hot gases and vapors by indirect heat interchange withthe cooling medium whereby the cooling medium is kept boiling. and thegases and vapors are cooled below the dew point of condensable oilconstituents,

and then cooling the remaining. gases and vapors to separate carbolicoil therefrom.

4. The method of distillingtar and lrecovering distillate, whichcomprises distilll ing coal tar in a current of inert gases,bringinterchange with a body of coal tar naphtha having a boiling rangeof 1GO-175Q C, whereby the naphtha is kept boiling and the gases arecooled to 170-185 C. and heavy creosote oil is separated from the gasesand then cooling the resulting gases and vapors by indirect heatinterchange with a body of toluol whereby thetoluol is kept boiling andthe gases are cooled to kabout 115o C. and light creosote oil isseparated from the gases.

5. The method of cooling a mixture of gases and vapors resulting fromthe inert gas distillation of tar to condense oils while leavingcarbolic oil in vapor form in the gases, which comprises bringing thehot gases and vapors into indirect heat interchange relation with aliquid having substantially the same boiling point as toluol therebykeeping the liquid boiling and condensing oils from admixture with thegases.

In testimony whereof I affix my signature.

EDWARD H. ELLMS.

ing the resulting gases and vapors 'into heat

